1. Field of the Invention
The present invention relates to a double-sided driving silent chain that engages with sprockets with inner and outer sides of the endless silent chain and more specifically to a double-sided driving silent chain using double-sided driving link plates each having teeth on both upper and lower sides thereof and to a silent chain transmission using the same.
2. Description of Related Art
Lately, a silent chain is being put into practical use as a timing chain for transmitting rotation of an engine crankshaft to a cam shaft as well as to a shaft of auxiliary units such as an oil pump and to that end, there is being proposed a double-sided driving silent chain that engages with sprockets with both inner and outer sides of the chain.
While there are the following types of double-sided driving silent chains, i.e., one that is provided with both inner side driving link trains in which link plates are arranged so that their teeth face to the inner side and outer side driving link trains in which link plates are arranged so that their teeth face to the outer side as disclosed in Japanese Patent Laid-open No. 2006-242329 for example and another one that uses double-sided driving link plates having teeth on both upper and lower sides of each link plate (facing respectively to the both outer and inner sides of the chain) as disclosed in Japanese Patent Laid-open No. Hei. 11-236950 for example, the present invention relates to the silent chain using the double-sided driving link plates.
As shown in FIG. 10, the conventional double-sided driving link plate 1 has a shape in which teeth sides of single-sided link plates are coupled symmetrically about a line L-L connecting centers of pin holes 2. The link plate 1 has, at its lower part, a pair of teeth 3, inner flanks 4 formed in a part (crotch) between the both teeth and outer flanks 5 formed on outer faces of the respective teeth and at its upper part, a pair of teeth 3′, inner flanks 4′ formed in a part (crotch) between the both teeth and outer flanks 5 formed on outer faces of the respective teeth in the same manner with the lower part. The double-sided driving silent chain is formed by endlessly linking the double-sided driving link plates 1 alternately by pins inserted into the pin holes 2 while placing guide link plates fixed with the pins at outermost sides of the double-sided driving link plates (see Japanese Patent Laid-open No. Hei. 11-236950).
While a width B of the double-sided driving link plate 1 at part between bottoms of the upper and lower crotches 6 and 6′ is narrow and a plate cross-sectional area (width B×plate thickness t) of the width part is a risky sectional area that has important implications in terms of strength of the plate, it is difficult to assure enough plate strength with respect to the link plate 1 having the symmetrical shape as described above.
Still more, while the silent chain using the double-sided driving link plates 1 contacts with a guide arm or a shoe of a lever by its outer circumferential face, an area of contact of the link plate with the shoe or the like has important implications in terms of advancement of wear of the link plate, shoe and others and affects a life of the silent chain. However, the symmetrical link plate 1 described above has the teeth 3 and 3′ having the same edge portions in the lower and upper parts thereof (i.e., on both inner and outer circumferential faces of the silent chain) and the contact area of the edge portion of the curved teeth 3′ is very small, so that the wear of the shoe, guide and others advances quickly and it is difficult to assure an enough life as a silent chain transmission.
Accordingly, the present invention seeks to provide a double-sided driving silent chain, and a double-sided driving silent chain transmission using the same, capable of solving the aforementioned problems by using a double-sided driving link plate formed so that its upper and lower parts are asymmetrical.